JP5659633B2 - Surface treatment method for stainless steel sheet - Google Patents
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- JP5659633B2 JP5659633B2 JP2010190732A JP2010190732A JP5659633B2 JP 5659633 B2 JP5659633 B2 JP 5659633B2 JP 2010190732 A JP2010190732 A JP 2010190732A JP 2010190732 A JP2010190732 A JP 2010190732A JP 5659633 B2 JP5659633 B2 JP 5659633B2
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- 238000000034 method Methods 0.000 title claims description 43
- 239000010935 stainless steel Substances 0.000 title claims description 41
- 229910001220 stainless steel Inorganic materials 0.000 title claims description 41
- 238000004381 surface treatment Methods 0.000 title claims description 18
- 230000010287 polarization Effects 0.000 claims description 28
- 238000007743 anodising Methods 0.000 claims description 25
- 239000008151 electrolyte solution Substances 0.000 claims description 11
- 238000010408 sweeping Methods 0.000 claims description 10
- 150000003839 salts Chemical class 0.000 claims description 9
- 230000009467 reduction Effects 0.000 claims description 8
- 239000003792 electrolyte Substances 0.000 claims description 7
- 230000007935 neutral effect Effects 0.000 claims description 6
- 238000005260 corrosion Methods 0.000 description 33
- 230000007797 corrosion Effects 0.000 description 33
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 26
- 230000008569 process Effects 0.000 description 15
- 238000012360 testing method Methods 0.000 description 15
- 229910000831 Steel Inorganic materials 0.000 description 13
- 239000000243 solution Substances 0.000 description 13
- 239000010959 steel Substances 0.000 description 13
- 238000005259 measurement Methods 0.000 description 6
- 239000000203 mixture Substances 0.000 description 5
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 4
- 238000002048 anodisation reaction Methods 0.000 description 4
- 230000000694 effects Effects 0.000 description 4
- 239000007788 liquid Substances 0.000 description 4
- 230000003647 oxidation Effects 0.000 description 4
- 238000007254 oxidation reaction Methods 0.000 description 4
- 229920006395 saturated elastomer Polymers 0.000 description 4
- KRVSOGSZCMJSLX-UHFFFAOYSA-L chromic acid Substances O[Cr](O)(=O)=O KRVSOGSZCMJSLX-UHFFFAOYSA-L 0.000 description 3
- 239000011651 chromium Substances 0.000 description 3
- AWJWCTOOIBYHON-UHFFFAOYSA-N furo[3,4-b]pyrazine-5,7-dione Chemical compound C1=CN=C2C(=O)OC(=O)C2=N1 AWJWCTOOIBYHON-UHFFFAOYSA-N 0.000 description 3
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 description 2
- 239000002253 acid Substances 0.000 description 2
- 239000011248 coating agent Substances 0.000 description 2
- 238000000576 coating method Methods 0.000 description 2
- 230000007423 decrease Effects 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- ZOMNIUBKTOKEHS-UHFFFAOYSA-L dimercury dichloride Chemical class Cl[Hg][Hg]Cl ZOMNIUBKTOKEHS-UHFFFAOYSA-L 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 238000000691 measurement method Methods 0.000 description 2
- 239000011259 mixed solution Substances 0.000 description 2
- 238000007747 plating Methods 0.000 description 2
- 238000005498 polishing Methods 0.000 description 2
- 238000012545 processing Methods 0.000 description 2
- 230000003252 repetitive effect Effects 0.000 description 2
- 239000011780 sodium chloride Substances 0.000 description 2
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 1
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 1
- 239000004115 Sodium Silicate Substances 0.000 description 1
- 150000007513 acids Chemical class 0.000 description 1
- 229910000147 aluminium phosphate Inorganic materials 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 229910052804 chromium Inorganic materials 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000004070 electrodeposition Methods 0.000 description 1
- 238000005868 electrolysis reaction Methods 0.000 description 1
- 238000010828 elution Methods 0.000 description 1
- 239000000395 magnesium oxide Substances 0.000 description 1
- CPLXHLVBOLITMK-UHFFFAOYSA-N magnesium oxide Inorganic materials [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 description 1
- AXZKOIWUVFPNLO-UHFFFAOYSA-N magnesium;oxygen(2-) Chemical compound [O-2].[Mg+2] AXZKOIWUVFPNLO-UHFFFAOYSA-N 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- MEFBJEMVZONFCJ-UHFFFAOYSA-N molybdate Chemical compound [O-][Mo]([O-])(=O)=O MEFBJEMVZONFCJ-UHFFFAOYSA-N 0.000 description 1
- VLAPMBHFAWRUQP-UHFFFAOYSA-L molybdic acid Chemical compound O[Mo](O)(=O)=O VLAPMBHFAWRUQP-UHFFFAOYSA-L 0.000 description 1
- 229910017604 nitric acid Inorganic materials 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 239000011734 sodium Substances 0.000 description 1
- NTHWMYGWWRZVTN-UHFFFAOYSA-N sodium silicate Chemical compound [Na+].[Na+].[O-][Si]([O-])=O NTHWMYGWWRZVTN-UHFFFAOYSA-N 0.000 description 1
- 229910052911 sodium silicate Inorganic materials 0.000 description 1
- 239000002436 steel type Substances 0.000 description 1
- 238000010998 test method Methods 0.000 description 1
- 230000007704 transition Effects 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
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Description
本発明は、無塗装で使用されるステンレス鋼板およびステンレスクラッド鋼板の耐食性（特に耐孔食性）や耐候性を向上させるステンレス鋼板の表面処理方法に関するものである。 The present invention relates to a surface treatment method for a stainless steel plate that improves the corrosion resistance (particularly pitting corrosion resistance) and weather resistance of stainless steel plates and stainless clad steel plates that are used without coating.
ステンレス鋼板の耐食性や耐候性を高めるために従来から知られている代表的な表面処理方法としては、めっき法のような、電析により表面にクロム等の金属皮膜を形成させる技術がある。
しかしながら、この技術は、処理液として硫酸のほかに高濃度のクロム酸等を使用するため、環境を考慮した廃液処理のコストが高いとともに、表面処理に必要な消費電力量が多く、処理時間が長いため、処理コストが高くなるといった問題がある。
As a typical surface treatment method conventionally known for improving the corrosion resistance and weather resistance of a stainless steel sheet, there is a technique for forming a metal film such as chromium on the surface by electrodeposition, such as plating.
However, since this technology uses high-concentration chromic acid in addition to sulfuric acid as the treatment liquid, the cost of waste liquid treatment considering the environment is high, the power consumption required for surface treatment is large, and the treatment time is high. Since it is long, there is a problem that the processing cost increases.
そこで、めっき法に代わる方法として、ステンレス鋼板を陰極とする電気化学的処理（陰極処理）の技術が、例えば、特許文献１〜３などに開示されている。これらの方法は、クロム酸、硫酸、リン酸等の溶液もしくはこれらの混合溶液中にさらに酸化マグネシウム、ケイ酸ソ−ダ、モリブデン酸塩等を添加した溶液を処理液として陰極処理し、表面に耐食性皮膜を形成する技術である。
Therefore, as an alternative to the plating method, a technique of electrochemical treatment (cathode treatment) using a stainless steel plate as a cathode is disclosed in, for example,
しかしながら、特許文献１〜３の方法では、モリブデン酸等の酸を使うため溶液の濃度管理が困難である。また、いずれの方法も、耐食性が不十分であり、光沢が低下し、意匠性を重視して無垢で使用するダル仕上げやヘアライン仕上げステンレス鋼板へ適用するには不適当であるという問題がある。
However, in the methods of
本発明は、かかる事情に鑑み、耐食性（特に耐孔食性）、耐候性を向上させるステンレス鋼板の表面処理方法を提供することを目的とする。 In view of such circumstances, an object of the present invention is to provide a surface treatment method for a stainless steel plate that improves corrosion resistance (particularly pitting corrosion resistance) and weather resistance.
本発明は、前記課題を解決するために、処理時間が短い電解溶液による定電位電解処理に着目し、詳細な検討を行った。その結果、表面処理方法として、ステンレス鋼板を陽極として電解溶液中で陽極酸化処理する方法を用い、陽極酸化処理するにあたり、耐孔食性が高い電位をあらかじめ求めておき、この電位にて定電位保持することによって、所期の目的が達成できるとの知見を得て、本発明を完成するに至った。 In order to solve the above problems, the present invention has been studied in detail with a focus on constant-potential electrolytic treatment with an electrolytic solution having a short treatment time. As a result, as a surface treatment method, a method of anodizing in an electrolytic solution using a stainless steel plate as an anode was used. In performing anodization, a potential with high pitting corrosion resistance was obtained in advance, and a constant potential was maintained at this potential. As a result, knowledge that the intended purpose can be achieved was obtained, and the present invention was completed.
本発明は、以上の知見に基づいてなされたものであり、その要旨は以下のとおりである。
［１］ステンレス鋼板を陽極として電解溶液中で陽極酸化処理するステンレス鋼板の表面処理方法であり、前記陽極酸化処理を行うにあたり、前記陽極酸化処理と同じ条件で、不動態域と過不動態域の境界電位まで掃引しながらアノード分極曲線を測定する処理を、電流密度：100μＡ／ｃｍ2 の電位が飽和に達するまで繰り返し行い、上記にて得られたアノード分極曲線をもとに、電流密度：100μＡ／ｃｍ2 における飽和電位を求め、次いで、得られた前記飽和電位に保持する前記陽極酸化処理を少なくとも1回行うことを特徴とするステンレス鋼板の表面処理方法。
［２］前記［１］において、陽極酸化処理を行う前に、陰極還元処理を行うことを特徴とするステンレス鋼板の表面処理方法。
［３］前記［１］または［２］において、前記電解溶液として中性塩電解液を使用することを特徴とするステンレス鋼板の表面処理方法。
This invention is made | formed based on the above knowledge, The summary is as follows.
[1] A surface treatment method for a stainless steel plate that is anodized in an electrolytic solution using a stainless steel plate as an anode, and in performing the anodizing treatment, under the same conditions as the anodizing treatment, a passive region and a hyperpassive region The process of measuring the anodic polarization curve while sweeping to the boundary potential is repeated until the potential of current density: 100 μA / cm 2 reaches saturation, and based on the anodic polarization curve obtained above, the current density: A method for treating the surface of a stainless steel sheet, comprising: obtaining a saturation potential at 100 μA / cm 2 , and then performing the anodizing treatment for maintaining the obtained saturation potential at least once.
[2] The surface treatment method for a stainless steel plate according to [1], wherein a cathode reduction treatment is performed before the anodization treatment.
[3] A surface treatment method for a stainless steel plate according to [1] or [2], wherein a neutral salt electrolyte is used as the electrolyte.
なお、本明細書において、対象とする鋼板は、ステンレス鋼板およびステンレスクラッド鋼板であり、以下、称して、ステンレス鋼板とする。 In addition, in this specification, the steel plate made into object is a stainless steel plate and a stainless clad steel plate, and hereafter is called a stainless steel plate.
本発明によれば、美観を損なわず、かつ、電解処理液の管理に格段な困難性を伴うことなく、ステンレス鋼板の耐食性（特に耐孔食性）および耐候性を向上させることが可能な表面処理方法を提供することができる。したがって、本発明の表面処理方法を用いることで、最近、需要増加が著しいダル仕上げや研磨仕上げ（ヘアライン仕上げ等）といった種々の表面仕上げの、無塗装使用ステンレス鋼板の耐食性および耐候性を向上させることができる。そのメカニズムは明確にされているとは言い難いが、電解処理により鋼板表面の可溶性析出物（例えばMnS）が除去されることに加えて、鋼板表面に形成された不動態皮膜中のCr濃縮割合が向上し、特に初期発銹軽減に好適なステンレス鋼板が容易に製造可能になると考えられる。
また、本発明によれば、従来の陰極処理と異なり、母材の組成に応じ表面皮膜の組成が異なるので、自己修復能があることも期待できることは言うまでもない。
According to the present invention, a surface treatment capable of improving the corrosion resistance (particularly pitting corrosion resistance) and weather resistance of a stainless steel sheet without impairing the aesthetics and without accompanying the difficulty of managing the electrolytic treatment liquid. A method can be provided. Therefore, by using the surface treatment method of the present invention, it is possible to improve the corrosion resistance and weather resistance of uncoated stainless steel sheets with various surface finishes such as dull finish and polishing finish (hairline finish, etc.) that have recently been increasing in demand. Can do. The mechanism is hard to clarify, but in addition to removing soluble precipitates (eg MnS) on the steel sheet surface by electrolytic treatment, the Cr concentration ratio in the passive film formed on the steel sheet surface It is considered that a stainless steel plate particularly suitable for reducing the initial cracking can be easily manufactured.
In addition, according to the present invention, unlike the conventional cathodic treatment, the composition of the surface film differs depending on the composition of the base material, so that it is needless to say that self-healing ability can be expected.
本発明は、ステンレス鋼板表面に耐食性皮膜を形成することで、ステンレス鋼板の耐食性および耐候性を向上させる表面処理方法である。そして、本発明では、表面処理方法として、ステンレス鋼板を陽極として電解溶液中で陽極酸化処理する方法を用いる。さらに、陽極酸化処理にあたり、陽極酸化処理と同じ条件で、不動態域と過不動態域の境界電位まで掃引しながらアノード分極曲線を測定する処理を、電流密度：100μＡ／ｃｍ2 の電位が飽和に達するまで繰り返し行い、上記にて得られたアノード分極曲線をもとに、電流密度：100μＡ／ｃｍ2 における飽和電位を求め、次いで、得られた前記飽和電位で定電位保持する陽極酸化処理を少なくとも1回行うことを特徴とする。
さらに、陽極酸化処理を行う前に、陰極還元処理を行うことが好ましい。
また、電解溶液として中性塩電解液を使用することが好ましい。
The present invention is a surface treatment method for improving the corrosion resistance and weather resistance of a stainless steel plate by forming a corrosion-resistant film on the surface of the stainless steel plate. In the present invention, as the surface treatment method, a method of anodizing in an electrolytic solution using a stainless steel plate as an anode is used. Furthermore, in the anodizing process, the process of measuring the anodic polarization curve while sweeping to the boundary potential between the passive region and the hyperpassive region under the same conditions as the anodizing treatment, the potential of current density: 100 μA / cm 2 is saturated. The saturation potential at a current density of 100 μA / cm 2 is obtained based on the anodic polarization curve obtained above, and then the anodic oxidation treatment is performed to maintain the constant potential at the obtained saturation potential. It is characterized in that it is performed at least once.
Furthermore, it is preferable to perform a cathodic reduction treatment before the anodizing treatment.
Moreover, it is preferable to use a neutral salt electrolyte as the electrolytic solution.
以下に、本発明を詳細に説明する。 The present invention is described in detail below.
ステンレス鋼板のアノード分極曲線の測定方法については、JIS G 0579に定められている。図1は、上記JIS G 0579の測定方法に従い、求めたアノード分極曲線を模式的に示したものである。アノード分極曲線は、図1に示すように、電位（E）の増加にともなって活性域のピーク(図1中（２）で表記)を過ぎたあと、不動態域（（３）〜（６））、過不動態域（（７）、（８））へと遷移する曲線を描く。 The method for measuring the anodic polarization curve of the stainless steel sheet is defined in JIS G 0579. FIG. 1 schematically shows an anodic polarization curve obtained according to the measurement method of JIS G 0579. As shown in FIG. 1, the anodic polarization curve passes the active region peak (indicated by (2) in FIG. 1) as the potential (E) increases, and then passes through the passive region ((3) to (6). )), Draw a curve that transitions to the hyperpassive zone ((7), (8)).
そこで、ステンレス鋼板（SUS436L）を用い、5.0mass％硫酸溶液（液温：30℃）中で、0.5Ｖ／min の掃引速度で、陽極酸化処理の最大電位（以下、掃引最終電位と称す）を図1の（１）〜（８）の各電位までとして、耐孔食性試験を行った。耐孔食性試験は、3.5mass％ＮａCｌ、30℃で行い、孔食電位Ｖ’ｃ100（電流密度100μＡ／ｃｍ2 のときの電位）を測定した。単位：ｍＶ vs SCE は飽和カロメル標準電極に対する電位を意味する。孔食電位Ｖ’ｃ100におよぼす掃引最終電位の影響を図2に示す。図2において、横軸の掃引最終電位（１）〜（８）は、図1にて表記される（１）〜（８）の電位に相当する。図2より、孔食電位Ｖ’ｃ100が最も高く耐孔食性が最も優れているのは掃引最終電位が（６）の場合であり、すなわち、図1において、不動態域と過不動態域の境界に相当する電位で陽極酸化処理した場合であることがわかる。一方、掃引最終電位が（８）の場合では、耐孔食性が低下している。掃引最終電位が（８）の場合とは、図1において、過不動態域の電位であり、1000μＡ／ｃｍ2 を超える電流密度に相当する電位である。ここでは、ステンレス鋼板表面に生成された不動態皮膜中のCr濃縮割合が低下し、耐食性が低下すると考えられる。 Therefore, using a stainless steel plate (SUS436L), the maximum potential of the anodizing treatment (hereinafter referred to as the final sweep potential) at a sweep rate of 0.5 V / min in a 5.0 mass% sulfuric acid solution (liquid temperature: 30 ° C.) The pitting corrosion resistance test was performed up to each potential of (1) to (8) in FIG. The pitting corrosion resistance test was performed at 3.5 mass% NaCl at 30 ° C., and the pitting corrosion potential V′c 100 (potential at a current density of 100 μA / cm 2 ) was measured. Unit: mV vs SCE means potential with respect to a saturated calomel standard electrode. The influence of the final sweep potential on the pitting potential V′c 100 is shown in FIG. In FIG. 2, the final sweep potentials (1) to (8) on the horizontal axis correspond to the potentials (1) to (8) shown in FIG. From FIG. 2, the pitting corrosion potential V′c 100 is the highest and the pitting corrosion resistance is the best when the sweep final potential is (6), that is, in FIG. It can be seen that this is the case where the anodization is performed at a potential corresponding to the boundary. On the other hand, when the final sweep potential is (8), the pitting corrosion resistance is reduced. The case where the final sweep potential is (8) is the potential in the overpassive region in FIG. 1, which corresponds to a current density exceeding 1000 μA / cm 2 . Here, it is considered that the Cr concentration ratio in the passive film formed on the surface of the stainless steel plate decreases, and the corrosion resistance decreases.
以上から、耐孔食性が優れているのは、不動態域と過不動態域の境界に相当する電位で陽極酸化処理した場合であることがわかった。そこで、本発明では、陽極酸化処理する際の定電位保持する電位として耐孔食性が高い不動態域と過不動態域の境界電位を用いることとする。 From the above, it was found that pitting corrosion resistance is excellent when anodizing is performed at a potential corresponding to the boundary between the passive region and the hyperpassive region. Therefore, in the present invention, a boundary potential between a passive region and a hyperpassive region having high pitting corrosion resistance is used as a potential to be held at a constant potential when anodizing.
次に、定電位保持する耐孔食性が高い電位の求め方について説明する。
上述したように、耐孔食性が高いのは、不動態域と過不動態域の境界電位である。そのため、不動態域と過不動態域の境界電位まで掃引しながらアノード分極曲線を測定する必要がある。
Next, a description will be given of how to obtain a potential with high pitting corrosion resistance that maintains a constant potential.
As described above, the pitting corrosion resistance is high at the boundary potential between the passive region and the hyperpassive region. Therefore, it is necessary to measure the anodic polarization curve while sweeping to the boundary potential between the passive region and the hyperpassive region.
図3は、ステンレス鋼板（SUS436L）について、5.0mass％硫酸溶液中、30℃で、−0.5 Ｖ VS SCEにおいて600sec保持する陰極還元処理を行った後、同溶液中で電位の増加方向に、0.5 Ｖ／min の掃引速度で、掃引しながらアノード分極曲線を測定する処理を10回まで繰り返した場合の、各回のアノード分極曲線の測定結果を示した図である。
図3から、繰り返して処理を行うことで、電位は希な方向にずれ、やがてそのずれは回数を追う毎に差がなくなり飽和することがわかる。繰り返し回数と所定の電流密度に到達する電位の変化は繰り返し数依存性があり、目的の使用溶液、温度条件における飽和点に近い電位が求められることがわかる。
FIG. 3 shows that a stainless steel plate (SUS436L) is subjected to cathodic reduction treatment at 600 ° C. in −0.5 V VS SCE in a 5.0 mass% sulfuric acid solution at 30 ° C. It is the figure which showed the measurement result of each anodic polarization curve at the time of repeating the process which measures an anodic polarization curve, sweeping up to 10 times at the sweep rate of V / min.
From FIG. 3, it can be seen that, by repeatedly performing the process, the potential shifts in a rare direction, and eventually the shift becomes saturated as the number of times increases. It can be seen that the number of repetitions and the change in potential reaching a predetermined current density are dependent on the number of repetitions, and a potential close to the saturation point in the intended use solution and temperature conditions is required.
以上のように、掃引処理を１回とし、この1回のアノード分極曲線の測定にて決定した電位を定電位保持する電位としても陽極電解処理の効果は得られる。しかし、より大きな効果を得るためには、同じ条件にて繰り返して掃引しアノード分極曲線を測定する処理を行い、目的とする使用溶液、温度条件における飽和点に近い電位を求めてその電位で定電位保持することが、耐食性および耐候性に優れた皮膜を鋼板表面に形成する点から最も効果的である。 As described above, the effect of the anodic electrolytic treatment can be obtained even when the sweep process is performed once and the potential determined by the measurement of the single anodic polarization curve is maintained at a constant potential. However, in order to obtain a greater effect, a process of repeatedly sweeping under the same conditions and measuring the anodic polarization curve is performed, and a potential close to the saturation point in the intended use solution and temperature conditions is obtained and determined at that potential. Holding the potential is most effective from the viewpoint of forming a coating having excellent corrosion resistance and weather resistance on the surface of the steel sheet.
繰り返して処理を行い飽和点に近い電位を求めるにあたって、基準は、アノード分極曲線における電流密度：100μＡ／ｃｍ2 に相当する電位とする。これは、電流密度：100μＡ／ｃｍ2 に相当する電位は不動態域を超えて不動態域と過不動態域の境界の電位にあたり、電流密度：100μＡ／ｃｍ2 に相当する電位を飽和電位を求める際の基準とすれば、不動態域と過不動態域の境界を明確に判定することが可能となるためである。 In obtaining the potential close to the saturation point by repeating the treatment, the reference is a potential corresponding to the current density in the anodic polarization curve: 100 μA / cm 2 . This is because the potential corresponding to the current density: 100 μA / cm 2 exceeds the passive region and corresponds to the boundary between the passive region and the hyperpassive region, and the potential corresponding to the current density: 100 μA / cm 2 is set to the saturation potential. This is because it is possible to clearly determine the boundary between the passive region and the hyperpassive region as the standard for obtaining.
よって、本発明では、同じ条件にて不動態域と過不動態域の境界電位まで掃引しながらアノード分極曲線を測定する処理を、電流密度：100μＡ／ｃｍ2 の電位が飽和に達するまで繰り返し行い、電流密度：100μＡ／ｃｍ2 に相当する電位における繰り返し依存性が飽和する電位（以下、Ｅsと称す）を求めることとする。 Therefore, in the present invention, the process of measuring the anodic polarization curve while sweeping to the boundary potential between the passive region and the hyperpassive region under the same conditions is repeated until the potential at a current density of 100 μA / cm 2 reaches saturation. Current density: A potential (hereinafter referred to as Es) at which the repetition dependence at a potential corresponding to 100 μA / cm 2 is saturated is obtained.
さらに、繰り返し回数と電流密度が100μA/cm2に到達する電位の変化の繰り返し数依存性は鋼種（鋼成分）による差異はあるものの、5回でほぼ飽和値に到達することが、検討した結果わかった。図4は、ステンレス鋼板（SUS436L）について、予め求めたアノード分極曲線における電流密度：100μＡ／ｃｍ2 に相当する電位（掃引電位）を各回ごとに求め、これを掃引処理の繰り返し数に対してプロットしたものである。
図4より、掃引電位は5回程度の掃引回数でほぼ飽和してしまうことがわかる。
Furthermore, although the number of repetitions and the current density at which the current density reaches 100 μA / cm 2 , the number of repetitions depends on the steel type (steel composition), but the results show that the number of repetitions reaches a saturation value almost 5 times. all right. FIG. 4 shows a potential (sweep potential) corresponding to a current density of 100 μA / cm 2 in an anodic polarization curve obtained in advance for a stainless steel plate (SUS436L), which is plotted against the number of repetitions of the sweep process. It is a thing.
FIG. 4 shows that the sweep potential is almost saturated at the number of sweeps of about 5.
なお、不動態域と過不動態域の境界電位まで掃引しながらアノード分極曲線を測定する処理を複数回繰り返すことが設備上、もしくは作業効率上困難な場合には、１回目の定電位保持でも相当の効果は得られる。 If it is difficult for the equipment or work efficiency to repeat the process of measuring the anodic polarization curve while sweeping to the boundary potential between the passive region and the hyperpassive region, even if the first constant potential is maintained. A considerable effect can be obtained.
以上から、陽極酸化処理と同じ条件で、不動態域と過不動態域の境界電位まで掃引しながらアノード分極曲線を測定する処理を、電流密度：100μＡ／ｃｍ2 の電位が飽和に達するまで繰り返し行い、上記にて得られたアノード分極曲線をもとに、電流密度：100μＡ／ｃｍ2 における飽和電位を求めることとする。特に、繰り返し回数は5回以上が好ましい。 From the above, the process of measuring the anodic polarization curve while sweeping to the boundary potential between the passive region and the hyperpassive region under the same conditions as the anodic oxidation treatment is repeated until the potential at a current density of 100 μA / cm 2 reaches saturation. The saturation potential at a current density of 100 μA / cm 2 is determined based on the anodic polarization curve obtained above. In particular, the number of repetitions is preferably 5 or more.
次いで、求めた飽和電位で定電位保持する陽極酸化処理について説明する。
ステンレス鋼板を陽極として飽和電位で定電位保持する陽極酸化処理を少なくとも1回行う。このような処理を行うことで、ステンレス鋼板表面に、最も効率よく、不動態の耐食性皮膜を形成することができ、その結果、ステンレス鋼板の耐食性および耐候性を向上させることができる。
Next, an anodic oxidation process that maintains a constant potential at the obtained saturation potential will be described.
Anodizing treatment is performed at least once by using a stainless steel plate as an anode and maintaining a constant potential at a saturation potential. By performing such treatment, a passive corrosion-resistant film can be formed most efficiently on the surface of the stainless steel plate, and as a result, the corrosion resistance and weather resistance of the stainless steel plate can be improved.
陽極酸化処理に用いる電解溶液としては0.1〜30mass％の硫酸が挙げられる。硫酸のみ、もしくは硫酸をベ−スとする混合溶液を用いることができる。硫酸中でのアノ−ド分極曲線測定では、活性態のピ−ク電位が他の酸に比べ高く、効率良く表面に溶出皮膜を形成させることができる。硫酸をベ−スとした混合溶液に用いるものとしては、クロム酸や硝酸などが使用可能である。
また、中性塩電解液（Na2SO4）を用いることも可能である。中性塩電解液を用いることで、表面の汚れが落とされ光沢性があがる。中性塩電解液の濃度については1〜30mass％の範囲が好ましい。
Examples of the electrolytic solution used for the anodizing treatment include 0.1 to 30 mass% sulfuric acid. Only sulfuric acid or a mixed solution based on sulfuric acid can be used. In anodic polarization curve measurement in sulfuric acid, the peak voltage in the active state is higher than that of other acids, and an elution film can be efficiently formed on the surface. As a mixture solution based on sulfuric acid, chromic acid or nitric acid can be used.
A neutral salt electrolyte (Na 2 SO 4 ) can also be used. By using a neutral salt electrolyte, dirt on the surface is removed and gloss is increased. About the density | concentration of a neutral salt electrolyte solution, the range of 1-30 mass% is preferable.
電位を掃引する速度は特に限定はしない。しかし、１ｍＶ／min 〜10Ｖ/secが好ましい。1ｍＶ／min 未満の遅い速度で掃引すると陽極酸化の作業効率が悪くなる場合がある。一方、10Ｖ/secを超えると電位が不安定となり、安定な電解ができない場合がある。 The speed at which the potential is swept is not particularly limited. However, 1 mV / min to 10 V / sec is preferable. If the sweep is performed at a slow speed of less than 1 mV / min, the working efficiency of the anodic oxidation may be deteriorated. On the other hand, if it exceeds 10 V / sec, the potential becomes unstable and stable electrolysis may not be possible.
陽極酸化処理に先立って、陰極還元処理を施すことによりステンレス鋼表面を清浄化することができ、後工程の陽極酸化処理をより一層効果的に行うことが可能になる。この陰極還元処理の電解溶液を後工程の陽極酸化処理と同様の溶液を用いることで、効率よく陽極酸化処理、陽極酸化処理の一連の作業を行うことができる。また、例えば、電解溶液として硫酸濃度：0.1〜30mass％の溶液中で、電位を−0.5〜−1.0（好適には−0.7）Ｖ vs SCE （飽和カロメル電極基準）、また保持時間を1.0〜120sec（好適には600sec程度）とすることが好ましい。 Prior to the anodizing treatment, the surface of the stainless steel can be cleaned by performing a cathodic reduction treatment, and the anodizing treatment in the subsequent process can be performed more effectively. By using the same electrolytic solution for the cathodic reduction treatment as that for the anodizing treatment in the subsequent step, a series of operations of anodizing treatment and anodizing treatment can be performed efficiently. For example, in an electrolytic solution having a sulfuric acid concentration of 0.1 to 30 mass%, the potential is −0.5 to −1.0 (preferably −0.7) V vs SCE (saturated calomel electrode standard), and the holding time is 1.0 to 120 sec. (Preferably about 600 seconds) is preferable.
表面をNo. 4（＃150〜180砥粒研磨）に仕上げた、表１に示す成分組成からなるステンレス鋼板（鋼No.1、鋼No.3）及びステンレスクラッド鋼板（鋼No.2）を、表4に示す電解溶液中で、電位の増加方向に、0.5Ｖ／min の掃引速度で、不動態域と過不動態域の境界電位まで掃引しながらアノード分極曲線を測定した。表4に処理回数を示す。
次いで、上記アノード分極曲線から求めた電流密度：100μＡ／ｃｍ2 における飽和電位（一部は、940ｍＶ vs SCE）まで、電位の増加方向に、0.5Ｖ／min の掃引速度で、電位を掃引する、陽極酸化処理を行った。また、一部のものについては、上記陽極酸化処理の前に、陽極酸化処理と同じ溶液中で−0.5〜−0.8Ｖ VS SCEにおいて60sec間保持する陰極還元処理を行った。このように処理した後と、処理前のステンレス鋼の白色度、光沢度を調査比較したが、上記表面処理前後で差は認められなかった。
Stainless steel plates (steel No. 1, steel No. 3) and stainless clad steel plates (steel No. 2) with the composition shown in Table 1 and finished with No. 4 surface (# 150-180 abrasive polishing) In the electrolytic solution shown in Table 4, the anodic polarization curve was measured while sweeping to the boundary potential between the passive region and the hyperpassive region at a sweep rate of 0.5 V / min in the increasing direction of the potential. Table 4 shows the number of processes.
Next, the potential is swept at a sweep rate of 0.5 V / min in the increasing direction of the potential up to a saturation potential (partially 940 mV vs. SCE) at a current density obtained from the anode polarization curve of 100 μA / cm 2 . Anodizing treatment was performed. In addition, some of the materials were subjected to cathodic reduction treatment that was held for 60 seconds at −0.5 to −0.8 V VS SCE in the same solution as the anodizing treatment before the anodizing treatment. After the treatment, the whiteness and glossiness of the stainless steel before the treatment were investigated and compared, but no difference was observed before and after the surface treatment.
以上より得られた供試材について、表2に示す条件の塩乾式複合サイクル腐食試験（ＣＣＴ試験）、下記に示す孔食電位測定試験、1年間の大気暴露試験をそれぞれ行い、硫酸溶液、定電位保持電位（Es）、Esへの繰り返し保持回数との関係について調査した。塩乾式複合サイクル腐食試験（ＣＣＴ試験）及び大気暴露試験の結果は、表３により評価した。
孔食電位測定試験は、JIS G 0577の測定方法に従い、アルゴン脱気した3.5mass％ＮａCｌ溶液（30℃）中において行ない、5回の測定回数の平均値とした。なお、ここでは、孔食電位はアノード電流密度が100μＡ／ｃｍ2 に達した電位（Ｖ’ｃ100）で表している。
大気暴露試験は、JIS Z 2381の試験方法に従い、護岸壁から5ｍの位置、南向き地面に対して36度の傾きで暴露する条件において、試験片サイズを150mm×100mmとして１年間の暴露試験を行なった。
The specimens obtained above were subjected to a salt dry combined cycle corrosion test (CCT test) under the conditions shown in Table 2, a pitting corrosion potential measurement test shown below, and a one-year atmospheric exposure test. The relationship between the potential holding potential (Es) and the number of repeated holdings to Es was investigated. The results of the salt dry combined cycle corrosion test (CCT test) and the atmospheric exposure test were evaluated according to Table 3.
The pitting potential measurement test was performed in a 3.5 mass% NaCl solution (30 ° C.) degassed with argon according to the measurement method of JIS G 0577, and the average value of five measurements was taken. Here, the pitting corrosion potential is represented by a potential (V′c 100 ) at which the anode current density reaches 100 μA / cm 2 .
In the air exposure test, in accordance with the test method of JIS Z 2381, a one-year exposure test was performed with a test piece size of 150 mm x 100 mm under the condition of exposure at a position of 5 m from the revetment wall and a slope of 36 degrees with respect to the south facing ground. I did it.
以上により得られた結果を表４に示す。
また、鋼No.１（SUS430）について、−0.5Ｖ VS SCE において600sec間の陰極還元処理後、５mass％硫酸溶液中で掃引速度５００ｍＶ／min で電位を１〜10回繰り返し掃引したときのアノ−ド分極曲線を図5に、同じ５mass％硫酸溶液中で、このアノ−ド分極曲線に基づいて、電流密度：100μＡ／ｃｍ2 に相当する電位に1secで掃引し、陽極酸化処理を1回から100回行った後のステンレス鋼の塩乾湿複合サイクル試験における発銹面積率を調査した結果を図６に示す。
Table 4 shows the results obtained as described above.
For steel No. 1 (SUS430), after an anode reduction treatment of -0.5V VS SCE for 600 seconds, the potential when the potential was repeatedly swept 1 to 10 times in a 5 mass% sulfuric acid solution at a sweep rate of 500 mV / min. Fig. 5 shows the current polarization curve in the same 5 mass% sulfuric acid solution. Based on this anodic polarization curve, the current density was swept at a potential corresponding to 100 µA / cm 2 in 1 second , and the anodization treatment was started once. FIG. 6 shows the results of investigating the glazing area ratio in a combined cycle test of stainless steel after 100 times of stainless steel.
表４、図５、図6から、本発明法により処理したステンレス鋼板及びステンレスクラッド鋼板は、表面性状に優れ、しかも耐食性とくに耐孔食性、耐候性に優れていることがわかる。 From Table 4, FIG. 5, and FIG. 6, it can be seen that the stainless steel plate and the stainless clad steel plate treated by the method of the present invention have excellent surface properties and excellent corrosion resistance, particularly pitting corrosion resistance and weather resistance.
Claims (3)
前記陽極酸化処理を行うにあたり、前記陽極酸化処理と同じ条件で、不動態域と過不動態域の境界電位まで掃引しながらアノード分極曲線を測定する処理を、電流密度：１００μＡ／ｃｍ２の電位が飽和に達するまで繰り返し行い、
上記にて得られたアノード分極曲線をもとに、電流密度：１００μＡ／ｃｍ２における飽和電位を求め、
次いで、得られた前記飽和電位で定電位保持する前記陽極酸化処理を少なくとも１回行うことを特徴とするステンレス鋼板の表面処理方法。 It is a surface treatment method of a stainless steel plate that is anodized in an electrolytic solution using a stainless steel plate as an anode,
In performing the anodizing treatment, a treatment for measuring an anodic polarization curve while sweeping to the boundary potential between the passive region and the hyperpassive region under the same conditions as in the anodizing treatment is performed. A potential of current density: 100 μA / cm 2 is used. Until it reaches saturation,
Based on the anodic polarization curve obtained above, the saturation potential at a current density of 100 μA / cm 2 was determined,
Next, the surface treatment method for a stainless steel sheet, wherein the obtained anodizing treatment is performed at least once to maintain a constant potential at the saturation potential.
ステンレス鋼板の表面処理方法。 The surface treatment method for a stainless steel plate according to claim 1, wherein a cathode reduction treatment is performed before the anodizing treatment.
のステンレス鋼板の表面処理方法。 The surface treatment method for a stainless steel plate according to claim 1 or 2, wherein a neutral salt electrolyte is used as the electrolyte.
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Free format text: JAPANESE INTERMEDIATE CODE: R250 |